In an internal combustion engine, when combustion occurs in an environment with excess oxygen, peak combustion temperatures increase, leading to the formation of unwanted emissions, such as NOx. This may be aggravated in internal combustion engine applications through the use of turbochargers operable to increase the mass of fresh air gas flow, and hence increase the concentrations of oxygen and nitrogen present in the combustion chamber of the engine when the temperature is high during or after a given combustion event.
Conventional NOx reduction techniques may be implemented, such as including a NOx emissions filter in-line with the exhaust stream. With such techniques, it is typically useful to determine the NOx content of the exhaust gas exiting the engine. The NOx content of the exhaust gas, produced by the engine, may be determined directly with a conventional NOx sensor. In typical applications, the NOx sensor is exposed to the exhaust gas to produce a signal that is, hopefully, indicative of the NOx content of the exhaust gas. In reality, however, the signal may be indicative of an unrepresentative, localized reading, and such readings are often times taken in a harsh environment, resulting in premature sensor failures.